If you don’t want to use firewalld, you can use straight nftables. You can convert your current ruleset to nftables equivalents as a starting point.
iptables-restore-translate
Otherwise if you want to do it in firewalld, you just need to use the right zones and right rules. For example, the gateway should be in external. The other LAN stuff can remain in say, internal.
Only other thing is you’ll need to setup ingress and egress rules. I would check out the page below.